System for additive manufacturing

ABSTRACT

A system is disclosed for additive manufacturing of a composite structure. The system may include an outlet through which a composite material is discharged, and a nose that is a component separate from the outlet and located at a distal end of the outlet. The nose may be biased axially relative to the outlet, from a retracted position to an extended position. The nose extends axially past the distal end of the outlet in the extended position.

RELATED APPLICATIONS

This application is based on and claims the benefit of priority from U.S. Provisional Application No. 62/769,498 that was filed on Nov. 19, 2018, the contents of which are expressly incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to a manufacturing system and, more particularly, to a system for manufacturing system.

BACKGROUND

Extrusion manufacturing is a known process for producing continuous structures. During extrusion manufacturing, a liquid matrix (e.g., a thermoset resin or a heated thermoplastic) is pushed through a die having a desired cross-sectional shape and size. The material, upon exiting the die, cures and hardens into a final form. In some applications, UV light and/or ultrasonic vibrations are used to speed the cure of the liquid matrix as it exits the die. The structures produced by the extrusion manufacturing process can have any continuous length, with a straight or curved profile, a consistent cross-sectional shape, and excellent surface finish. Although extrusion manufacturing can be an efficient way to continuously manufacture structures, the resulting structures may lack the strength required for some applications.

Pultrusion manufacturing is a known process for producing high-strength structures. During pultrusion manufacturing, individual fiber strands, braids of strands, and/or woven fabrics are coated with or otherwise impregnated with a liquid matrix (e.g., a thermoset resin or a heated thermoplastic) and pulled through a stationary die where the liquid matrix cures and hardens into a final form. As with extrusion manufacturing, UV light and/or ultrasonic vibrations are used in some pultrusion applications to speed the cure of the liquid matrix as it exits the die. The structures produced by the pultrusion manufacturing process have many of the same attributes of extruded structures, as well as increased strength due to the integrated fibers. Although pultrusion manufacturing can be an efficient way to continuously manufacture high-strength structures, the resulting structures may lack the form (shape, size, and/or precision) required for some applications. In addition, during conventional multi-fiber pultrusion, ensuring adequate wetting and bonding between adjacent fibers can be problematic.

The disclosed system is directed to addressing one or more of the problems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a system for additive manufacturing. The system may include an outlet through which a composite material is discharged, and a nose that is a component separate from the outlet and located at a distal end of the outlet. The nose may be biased axially relative to the outlet, from a retracted position to an extended position. The nose extends axially past the distal end of the outlet in the extended position.

In another aspect, the present disclosure is directed to another system for additive manufacturing. The system may include an outlet through which a composite material is discharged, and a nose that is a component separate from the outlet and located at a distal end of the outlet. A material forming the outlet may be harder than a material forming the nose. The nose may extend axially past the distal end of the outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric illustration of an exemplary disclosed additive manufacturing system; and

FIGS. 2, 3, 4, and 5 are cross-sectional illustrations of exemplary disclosed print heads that may be utilized with the additive manufacturing system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary system 10, which may be used to manufacture a composite structure 12 having any desired cross-sectional shape (e.g., ellipsoidal, polygonal, etc.). System 10 may include at least a moveable support 14 and a print head (“head”) 16. Support 14 may be coupled to and configured to move head 16. In the disclosed embodiment of FIG. 1, support 14 is a robotic arm capable of moving head 16 in multiple directions during fabrication of structure 12, such that a resulting longitudinal axis of structure 12 is three-dimensional. It is contemplated, however, that support 14 could alternatively be a gantry, a hybrid gantry/arm, or another type of movement system that is capable of moving head 16 in multiple directions during fabrication of structure 12. Although support 14 is shown as being capable of multi-axis movement (e.g., movement about six or more axes), it is contemplated that any other type of support 14 capable of moving head 16 in the same or in a different manner could also be utilized, if desired. In some embodiments, a drive may mechanically couple head 16 to support 14 and may include components that cooperate to move and/or supply power or materials to head 16.

Head 16 may be configured to receive or otherwise contain a matrix. The matrix may include any type of material (e.g., a liquid resin, such as a zero-volatile organic compound resin; a powdered metal; a solid filament; etc.) that is curable. Exemplary matrixes include thermosets, single- or multi-part epoxy resins, polyester resins, cationic epoxies, acrylated epoxies, urethanes, esters, thermoplastics, photopolymers, polyepoxides, thiols, alkenes, thiol-enes, reversible resins (e.g., Triazolinedione, a covalent-adaptable network, a spatioselective reversible resin, etc.) and more. In one embodiment, the matrix inside head 16 may be pressurized, for example by an external device (e.g., an extruder or another type of pump—not shown) that is fluidly connected to head 16 via a corresponding conduit (not shown). In another embodiment, however, the matrix pressure may be generated completely inside of head 16 by a similar type of device. In yet other embodiments, the matrix may be gravity-fed through and/or mixed within head 16. In some instances, the matrix inside head 16 may need to be kept cool and/or dark to inhibit premature curing; while in other instances, the matrix may need to be kept warm for similar reasons. In either situation, head 16 may be specially configured (e.g., insulated, temperature-controlled, shielded, etc.) to provide for these needs.

The matrix may be used to coat, encase, or otherwise at least partially surround or saturate (e.g., wet) any number of continuous reinforcements (e.g., separate fibers, tows, rovings, ribbons, and/or sheets of material) and, together with the reinforcements, make up at least a portion (e.g., a wall) of composite structure 12. The reinforcements may be stored within (e.g., on separate internal spools) or otherwise passed through head 16 (e.g., fed from one or more external spools). When multiple reinforcements are simultaneously used, the reinforcements may be of the same type and have the same diameter and cross-sectional shape (e.g., circular, square, flat, hollow, solid, etc.), or of a different type with different diameters and/or cross-sectional shapes. The reinforcements may include, for example, carbon fibers, vegetable fibers, wood fibers, mineral fibers, glass fibers, metallic wires, optical tubes, etc. It should be noted that the term “reinforcement” is meant to encompass both structural and non-structural types of continuous materials that can be at least partially encased in the matrix discharging from head 16.

The reinforcements may be exposed to (e.g., at least partially coated or impregnated with) the matrix while the reinforcements are inside head 16, while the reinforcements are being passed to head 16 (e.g., as a prepreg material), and/or while the reinforcements are discharging from head 16, as desired. The matrix, dry reinforcements, and/or reinforcements that are already exposed to the matrix (e.g., wetted reinforcements) may be transported into head 16 in any manner apparent to one skilled in the art.

The matrix and reinforcement may be discharged from head 16 via at least two different modes of operation. In a first mode of operation, the matrix and reinforcement are extruded (e.g., pushed under pressure and/or mechanical force) from head 16, as head 16 is moved by support 14 to create the 3-dimensional shape of structure 12. In a second mode of operation, at least the reinforcement is pulled from head 16, such that a tensile stress is created in the reinforcement during discharge. In this mode of operation, the matrix may cling to the reinforcement and thereby also be pulled from head 16 along with the reinforcement, and/or the matrix may be discharged from head 16 under pressure along with the pulled reinforcement. In the second mode of operation, where the matrix material is being pulled from head 16 with the reinforcement, the resulting tension in the reinforcement may increase a strength of structure 12 (e.g., by aligning the reinforcements, inhibiting buckling, equally distributing loads, etc.), while also allowing for a greater length of unsupported structure 12 to have a straighter trajectory (e.g., by creating moments that oppose gravity).

The reinforcement may be pulled from head 16 as a result of head 16 moving away from an anchor point 18. In particular, at the start of structure-formation, a length of matrix-impregnated reinforcement may be pulled and/or pushed from head 16, deposited onto a stationary or moveable anchor point 18, and cured, such that the discharged material adheres to anchor point 18. Thereafter, head 16 may be moved away from anchor point 18, and the relative movement may cause additional reinforcement to be pulled from head 16. It should be noted that the movement of the reinforcement through head 16 could be assisted (e.g., via internal feed mechanisms), if desired. However, the discharge rate of the reinforcement from head 16 may primarily be the result of relative movement between head 16 and anchor point 18, such that tension is created within the reinforcement.

Any number of reinforcements may be passed axially through head 16 and be discharged together with at least a partial coating of matrix. At discharge (or shortly thereafter), one or more cure enhancers (e.g., one or more light sources, ultrasonic emitters, lasers, heaters, catalyst dispensers, microwave generators, etc.) 20 may expose the matrix coating to a cure energy (e.g., light energy, electromagnetic radiation, vibrations, heat, a chemical catalyst or hardener, or other form of actively-applied energy). The cure energy may trigger a chemical reaction, increase a rate of chemical reaction already occurring within the matrix, sinter the material, harden the material, or otherwise cause the material to cure as it discharges from head 16.

A controller 22 may be provided and communicatively coupled with support 14, head 16, and/or any number and type of cure enhancers 20. Controller 22 may embody a single processor or multiple processors that include a means for controlling an operation of system 10. Controller 22 may include one or more general- or special-purpose processors or microprocessors. Controller 22 may further include or be associated with a memory for storing data such as, for example, design limits, performance characteristics, operational instructions, matrix characteristics, reinforcement characteristics, characteristics of structure 12, and corresponding parameters of each component of system 10. Various other known circuits may be associated with controller 22, including power supply circuitry, signal-conditioning circuitry, solenoid/motor driver circuitry, communication circuitry, and other appropriate circuitry. Moreover, controller 22 may be capable of communicating with other components of system 10 via wired and/or wireless transmission.

One or more maps may be stored in the memory of controller 22 and used during fabrication of structure 12. Each of these maps may include a collection of data in the form of models, lookup tables, graphs, and/or equations. In the disclosed embodiment, the maps are used by controller 22 to determine desired characteristics of cure enhancers 20, the associated matrix, and/or the associated reinforcements at different locations within structure 12. The characteristics may include, among others, a type, quantity, and/or configuration of reinforcement and/or matrix to be discharged at a particular location within structure 12, and/or an amount, intensity, shape, and/or location of desired curing. Controller 22 may then correlate operation of support 14 (e.g., the location and/or orientation of head 16) and/or the discharge of material from head 16 (a type of material, desired performance of the material, cross-linking requirements of the material, a discharge rate, etc.) with the operation of cure enhancers 20, such that structure 12 is produced in a desired manner.

Head 16 may be an assembly of multiple components that cooperate to discharge matrix-coated reinforcements. These components may include, among other things, a matrix reservoir 24 and an outlet (e.g., a nozzle) 26. Matrix reservoir 24 may be configured to hold a finite supply of matrix material sufficient to wet a desired length of reinforcements passing therethrough. In some embodiments, matrix reservoir 24 may be automatically replenished with matrix (e.g., based on a sensed amount of matrix remaining in reservoir 24). Outlet 26 may be located at a discharge end of matrix reservoir 24 and configured to receive the matrix-coated reinforcements therefrom. Cure enhancer(s) 20 may be mounted at the discharge end of matrix reservoir 24 and adjacent (e.g., at a trailing edge of and/or around) outlet 26.

An exemplary head 16 is disclosed in detail in FIGS. 2 and 3. As shown in these figures, outlet 26 of head 16 may include unique features that are configured to improve a quality of the material discharging from head 16. In particular, in some situations, it may be possible for the matrix-coated reinforcements to include voids (e.g., air bubbles), ridges, frayed ends, or other irregularities that inhibit adhesion between fibers or create uneven and rough surface textures. In these situations, compressing (e.g., pressing the material into an adjacent layer) the discharged material prior to and/or during curing may improve the quality of structure 12. For this purpose, a nose 30 may be slidingly located around outlet 26. Nose 30 may be configured to slide in an axial direction of outlet 26 between a retracted (i.e., non-compacting) position located closest to matrix reservoir 24 and extended (i.e., compacting) position located furthest from matrix reservoir 24. As shown in FIG. 2, nose 30 may extend axially past a terminal end of outlet 26 when at the extended location. As shown in FIG. 3, an outer end surface of nose 30 may be generally flush (e.g., within engineering tolerances) with the terminal end of outlet 26 during compacting of the matrix-coated reinforcements.

Nose 30 may be biased toward the extended position (e.g., via one or more springs 32). With this arrangement, nose 30 may ride over and exert a flattening or compacting force on the material discharging through outlet 26, just prior to the material being exposed to cure energy from cure enhancer(s) 20. The compressing force may function to press out air bubbles, improve resin impregnation, consolidate loose fibers, and otherwise smooth surface features.

In the embodiment of FIGS. 2 and 3, nose 30 is ring-like (e.g., annularly surrounding outlet 26) and flat at the outer end surface. A radial outer edge at the end surface may be rounded or chamfered, to reduce a likelihood of catching on, cutting, or otherwise damaging structure 12. Similarly, a radial inner edge at the end surface may also be rounded or chamfered to inhibit catching, cutting, or breaking of the continuous reinforcement passing therethrough, if desired. In these embodiments, nose 30 may have a complimentary shape (e.g., a continuing radius or chamfer), if desired.

A material that forms nose 30 may be relatively softer than a material forming outlet 26 (e.g., at least the nozzle tip), such that nose 30 may wear away faster than outlet 26. For example, the outlet material may be harder than the nose material by at least 10%, when using conventional hardness scales known in the art (e.g., when using the Brinell Hardness Scale, the Rockwell Hardness Scale, the Knoop Hardness Scale, the Vickers Hardness Scale, etc.). In one example, outlet 26 may be fabricated from stainless steel or aluminum, while nose 30 may be fabricated from rubber, plastic, or other polymer. In this arrangement, nose 30 may function as a replaceable sacrificial layer that protects outlet 26 from excessive wear.

While nose 30 may have a generally square cross-sectional shape in the embodiments of FIGS. 2 and 3, nose 30 could have other shapes, if desired. For example, FIG. 4 illustrates nose 30 as being conical or frustoconical, with a smaller axial end surface.

Over a period of use, nose 30 may wear away and no longer have a shape and/or texture required for efficiently engaging the material discharging through outlet 26. When this occurs, head 16 may be maneuvered (e.g., via support 14) over the top of a resurfacer 34 that is configured to restore an outer profile of nose 30 to a near-original shape, size, and/or texture. In the embodiment of FIG. 4, resurfacer 34 resembles a sharpener having one or more blades 36 that are positioned and/or oriented at precise locations for the particular configuration of nose 30. In other embodiments, however, resurfacer 34 could embody a sander, a hot iron, a mold, or another similar device.

It is contemplated that nose 30 may be coated with a substance that inhibits the matrix material from sticking to nose 30 during the compacting operation described above. For example, nose 30 may be coated with a release wax, petroleum jelly, a PTFE coating, etc. In this situation, resurfacer 34 may be further capable of reapplying that coating. For example, resurfacer 34 may include a spray jet, an orifice, or another mechanism (not shown) that advances the coating onto nose 30 when nose 30 is brought near and/or into contact with resurfacer 34. Resurfacer 34 may be mounted on or adjacent support 14 (referring to FIG. 1), for example connected to a build chamber floor, wall, or other similar structure.

FIG. 5 illustrates another embodiment of print head 16 that may be used in conjunction with system 10. In this embodiment, nose 30 does not annularly surround outlet 26. In contrast, nose 30 may be connected at an axial end of outlet 26 such that nose 30 functions as an extension of outlet 26. In this embodiment, since nose 30 may always protrude past outlet 26, springs 32 may be omitted. Resilience of nose 30, in this embodiment, may primarily be associated with the material of nose 30. For example, nose 30 may be fabricated from an elastomeric material. It should be noted, however, that an axial distance between the extended (i.e., non-compacting) and retracted (i.e., compacting) positions may be less for this embodiment.

INDUSTRIAL APPLICABILITY

The disclosed systems may be used to continuously manufacture composite structures having any desired cross-sectional size, shape, length, density, and/or strength. The composite structures may include any number of different reinforcements of the same or different types, diameters, shapes, configurations, and consists, each coated with a common matrix material. In addition, the disclosed heads may allow for compaction and/or smoothing of structural surfaces and, thereby, an increased strength and/or performance. Operation of system 10 will now be described in detail.

At a start of a manufacturing event, information regarding a desired structure 12 may be loaded into system 10 (e.g., into controller 22 that is responsible for regulating operations of support 14 and/or head 16). This information may include, among other things, a size (e.g., diameter, wall thickness, length, etc.), a contour (e.g., a trajectory), surface features (e.g., ridge size, location, thickness, length; flange size, location, thickness, length; etc.), connection geometry (e.g., locations and sizes of couplings, tees, splices, etc.), desired weave patterns, weave transition locations, location-specific matrix stipulations, location-specific reinforcement stipulations, density stipulations, etc. It should be noted that this information may alternatively or additionally be loaded into system 10 at different times and/or continuously during the manufacturing event, if desired. Based on the component information, one or more different reinforcements and/or matrix materials may be selectively installed and/or continuously supplied into system 10.

Installation of the reinforcements may be performed by passing the reinforcements down through matrix reservoir 24, and then threading the reinforcements through outlet 26 and nose 30. Installation of the matrix material may include filling head 16 and/or coupling of an extruder (not shown) to head 16.

Head 16 may then be moved by support 14 under the regulation of controller 22 to cause matrix-coated reinforcements to be placed against or on a corresponding anchor point 18. Cure enhancers 20 may then be selectively activated to cause hardening of the matrix material surrounding the reinforcements, thereby bonding the reinforcements to anchor point 18.

The component information may then be used to control operation of systems 10 and 12. For example, the reinforcements may be pulled and/or pushed from head 16 (along with the matrix material), while support 14 selectively moves head 16 in a desired manner during curing, such that an axis of the resulting structure 12 follows a desired trajectory (e.g., a free-space, unsupported, 3-D trajectory). As the separate reinforcements are pulled through head 16, the reinforcements may pass under nose 30 and be flattened and/or compressed into a desired thickness and/or contour. Once structure 12 has grown to a desired length, structure 12 may be disconnected (e.g., severed) from head 16 in any desired manner.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed systems and head. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed systems and heads. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A system for additively manufacturing, comprising: an outlet through which a composite material is discharged; and a nose that is a component separate from the outlet and located at a distal end of the outlet, wherein: the nose is biased axially relative to the outlet, from a retracted position to an extended position; and the nose extends axially past the distal end of the outlet in the extended position.
 2. The system of claim 1, further including at least one spring configured to bias the nose axially relative to the outlet.
 3. The system of claim 1, further including a matrix reservoir located at a side of the outlet opposite the nose, the matrix reservoir configured to wet a continuous reinforcement with a matrix to form the composite material.
 4. The system of claim 3, further including a cure enhancer configured to expose the matrix in the composite material to a cure energy after the nose has passed over the composite material.
 5. The system of claim 4, further including a support configured to move the matrix reservoir, the outlet, and nose together.
 6. The system of claim 5, further including a controller in communication with the cure enhancer and the support, the controller being configured to coordinate operations of the support and the cure enhancer based on specifications for a structure to be manufactured from the composite material.
 7. The system of claim 5, wherein the support is located at a side of the matrix reservoir opposite the outlet.
 8. The system of claim 1, wherein the nose annularly surrounds the distal end of the outlet.
 9. The system of claim 1, wherein the nose extends axially from the distal end of the outlet.
 10. The system of claim 1, further including a coating on an outer end surface of the nose, the coating configured to inhibit the composite material from sticking to the nose.
 11. The system of claim 1, wherein a material forming the outlet is harder than a material forming the nose.
 12. The system of claim 11, wherein: the material forming the outlet is one of stainless steel or aluminum; and the material forming the nose is a polymer.
 13. The system of claim 1, wherein during operation, an end surface of the nose is generally flush with an end surface of the outlet.
 14. The system of claim 1, further including a resurfacer configured to restore an outer profile of the nose.
 15. The system of claim 1, wherein the nose is biased via a material characteristic of the nose.
 16. The system of claim 15, wherein the nose is fabricated from an elastomeric material.
 17. The system of claim 1, wherein an outer radial edge at an axial end surface of the nose is at least one of rounded and chamfered.
 18. The system of claim 1, wherein an inner radial edge at an axial end surface of the nose is at least one of rounded and chamfered.
 19. The system of claim 18, wherein an inner radial edge of the outlet at the distal end has a shape complimentary to the inner radial edge at the axial end surface of the nose.
 20. A system for additively manufacturing, comprising: an outlet through which a composite material is discharged; and a nose that is a component separate from the outlet and located at a distal end of the outlet, wherein: a material forming the outlet is harder than a material forming the nose; and the nose extends axially past the distal end of the outlet. 